1. Field of the Invention
The present invention relates generally to an apparatus and method for transmitting/receiving data in a mobile communication system. In particular, the present invention relates to an apparatus and method for transmitting/receiving packet data in a mobile communication system.
2. Description of the Related Art
Mobile communication systems have been developed to provide voice services, guaranteeing the mobility of a user. With the rapid progress in communication technology, mobile communication systems have evolved into systems that are capable of providing data service as well. Recently, research has been conducted on high-speed data transmission in a Code Division Multiple Access (CDMA) mobile communication system. A 1× Evolution Data Only (1×EVDO) system is a typical mobile communication system having a channel structure for the high-speed data transmission. The 1×EVDO system was proposed in the 3rd Generation Partnership Project 2 (3GPP2) to complement data communication of the IS-2000 system.
In the 1×EVDO system, data communication can be divided into forward data communication and reverse data communication. The term “forward data communication” refers to data communication from an access network (or base station) to an access terminal (or mobile station), while the term “reverse data communication” refers to data communication from an access terminal to an access network. A description will now be made of exemplary structures of forward channels in the 1×EVDO system. The forward channels are classified as a pilot channel, a forward Medium Access Control (MAC) channel, a forward traffic channel, and a forward control channel, all of which are transmitted to an access terminal after being subjected to Time Division Multiplexing (TDM). A set of the TDM transmission signals is called a “burst.”
Among these channels, the forward traffic channel transmits a user data packet, and the forward control channel transmits a control message and a user data packet. In addition, the forward MAC channel is used for reverse rate control, transmission of power control information, and assignment of forward data channel.
A description will now be made of reverse channels used in the 1×EVDO system. Unlike the forward channels, the reverse channels used in the 1×EVDO system have different identification codes unique to access terminals. Therefore, in the following description, the “reverse channels” refer to channels transmitted to an access network with different identification codes unique to the access terminals. The reverse channels comprise a pilot channel, a reverse traffic channel, an access channel, a Data Rate Control (DRC) channel, and a Reverse Rate Indicator (RRI) channel.
Functions of the reverse channels will now be described in greater detail. The reverse traffic channel, like the forward traffic channel, transmits a user data packet in the reverse direction. The DRC channel is used to indicate a forward data rate that the access terminal can support, and the RRI channel is used to indicate a rate of a data channel transmitted in the reverse direction. The access channel is used when the access terminal transmits a message or traffic to the access network before the traffic channel is connected. With reference to FIG. 1, a description will now be made of a configuration of the 1×EVDO system, a rate control operation, and its associated channels.
FIG. 1 is a conceptual diagram illustrating a 1×EVDO mobile communication system.
Referring to FIG. 1, reference numeral 100 denotes access terminals (ATs), reference numeral 110 denotes access network transceiver systems (ANTSs), and reference numeral 120 denotes access network controllers (ANCs). A brief description of the system configuration will now be made. A first ANTS 110a communicates with a plurality of ATs 100a and 100b, and a second ANTS 110b communicates with an AT 100c. The first ANTS 110a is connected to a first ANC 120a, and the second ANTS 10b is connected to a second ANC 120b. Each of the ANCs 120a and 120b can be connected to two or more ANTSs. In FIG. 1, one ANC is connected to only one ANTS, as an example. The ANCs 120a and 120b are connected to a packet data service node (PDSN) 130 that provides a packet data service, and the PDSN 130 is connected to an Internet network 140.
In the exemplary mobile communication system of FIG. 1, each of the ANTSs 110a and 110b transmits packet data to only the AT having the highest packet data rate among the ATs located in its coverage. A detailed description thereof will now be made. In the following description, an AT will be denoted by reference numeral 100, and an ANTS will be denoted by reference numeral 110.
For rate control of a forward channel, an AT 100 measures reception strength of a pilot channel transmitted by an ANTS 110, and determines a forward data rate desired by the AT 100 according to a fixed value predetermined based on the measured pilot reception strength. Thereafter, the AT 100 transmits DRC information corresponding to the determined forward data rate to the ANTS 110 over a DRC channel. Then the ANTS 110 receives DRC information from all of the ATs intending to communicate therewith, located in its coverage. Based on the DRC information, the ANTS 110 can transmit packet data to only a particular AT having a good channel quality condition at a data rate reported by the AT. The DRC information refers to a value determined from a possible forward data rate calculated by the AT by measuring its channel condition. Although a mapping relationship between the forward channel condition and the DRC information is subject to change according to implementation, typically the mapping relationship is fixed in the manufacturing process of the AT.
The mapping relationship between the DRC value reported by an AT and its associated data rate and transmission format is shown in Table 1 below, by way of example.
TABLE 1Data RateNumber of TXTransmissionDRC(kbps)(slots)Format0x0016(1024, 16, 1024)0x138.416(1024, 16, 1024)0x276.88(1024, 8, 512)0x3153.64(1024, 4, 256)0x4307.22(1024, 2, 128)0x5307.24(2048, 4, 128)0x6614.41(1024, 1, 64)0x7614.42(2048, 2, 64)0x8921.62(3072, 2, 64)0x91228.81(2048, 1, 64)0xa1228.82(4096, 2, 64)0xb1843.21(3072, 1, 64)0xc2457.61(4096, 1, 64)0xd15362(5120, 2, 64)0xe30721(5120, 1, 64)
It can be noted from Table 1 that the transmission format is expressed in the form of (A, B, C). The transmission format will be described herein below with reference to a first field of Table 1, as an example. In the transmission format (A, B, C), C=1024 indicates 1024-bit information, B=16 indicates that the information is transmitted for 16 slots, and A=1024 indicates that a 1024-chip preamble is transmitted. Therefore, an ANTS transmits data to an AT with the transmission format corresponding to a DRC value reported by the AT. After reporting the DRC value, the AT attempts to receive a forward data channel only with the transmission format corresponding to the reported DRC value. This agreement is made because no other channel exists to indicate a data rate for a data channel transmitted in the forward direction. That is, when the ANTS transmits data using a transmission format other than the transmission format reported by the AT, there is no way to indicate the transmission format, so that the AT cannot receive the data. Therefore, the ANTS transmits data only with the transmission format corresponding to (compatible with) the DRC reported by the AT. For example, for an AT that transmitted DRC=0x01 over a DRC channel, the ANTS transmits data using a transmission format (1024, 16, 1024) corresponding to the DRC value, and the AT attempts to receive the data with only the transmission format of the corresponding DRC value.
The packet data that the ANTS transmits to one AT according to received DRC information in accordance with the method of Table 1 is called a “single user packet.” The ANTS transmits data using the single user packet for the general data service. Compared with the general data service, such a data service as voice-over-Internet protocol (VoTP) requires a lower transmission bandwidth of about 9.6 kbps, in which, data of about 192 bits is transmitted every 20 ms. However, transmitting the short data through the single user packet having a minimum size of 1024 bits causes unnecessary bandwidth waste. In order to prevent the resource waste in the wireless access section, a scheme for transmitting data for several users through one physical packet has been introduced, and this packet format is called a “multiuser packet.” The multiuser packet will now be described with reference to Table 2 below, by way of example.
TABLE 2RateList of AssociatedDRC(kbps)Multi-User Transmission Formats0x00(128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256)0x138.4(128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256)0x276.8(128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256)0x3153.6(128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256)0x4307.2(128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256)0x5307.2(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128)0x6614.4(128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256)0x7614.4(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128)0x8921.6(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128), (3072, 2, 64)0x91228.8(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128)0xa1228.8(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128),(3072, 2, 64), (4096, 2, 64)0xb1843.2(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128), (3072, 2, 64)0xc2457.6(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128),(3072, 2, 64), (4096, 2, 64)0xd1536(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128),(3072, 2, 64), (4096, 2, 64), (5120, 2, 64)0xe3072(128, 4, 256), (256, 4, 256), (512, 4, 256),(1024, 4, 256), (2048, 4, 128),(3072, 2, 64), (4096, 2, 64), (5120, 2, 64)
Table 2 illustrates an exemplary format of the multiuser packet for each DRC in the 1×EVDO system. In Table 2, each DRC index includes its associated data rate and a format of a packet to be transmitted to multiple users. A description thereof will be made with reference to a fifth field of Table 2, as an example. That is, a format of a multiuser packet transmitted to multiple ATs that transmitted DRC=5 is given as (128, 4, 256), (256, 4, 256), (512, 4, 256), (1024, 4, 256), (2048, 4, 128). This multiuser packet includes packet data for several users, and is transmitted together with the addresses of the ATs that will receive the packet data. An AT, upon receiving the multiuser packet, determines whether its own address is included in the received multiuser packet, and if its own address is included therein, processes a user packet corresponding thereto.
Although transmission of the multiuser packet is being discussed in 3GPP2 that has established the CDMA 1×EVDO standard, there is no discussion on how to transmit an address of the multiuser packet. Accordingly, there is a need for an apparatus and method that is capable of detecting the case where one packet is commonly transmitted to multiple users rather than a single user, and reporting the detection result to each of the users.